The present invention relates to the manufacture of semiconductor devices. More particularly, the present invention is directed to methods for selectively etching oxides to metal nitrides and metal oxides during manufacture of a semiconductor device.
During manufacture of components such as capacitors for use in semiconductor devices, there are many circumstances in which it is desirable to perform cleaning operations to remove native oxides or other oxide contaminants from one or more exposed surfaces. For example, when forming a double-sided container for a capacitor, a polysilicon or metal contact plug is formed. This is followed by deposition of an oxide layer such as BPSG (borophosphosilicate glass). Using conventional masking techniques, a container structure is formed by etching through the oxide layer to the contact plug. A spacer (sacrificial liner) formed of a metal oxide such as aluminum oxide is deposited along the container walls.
The spacer is then punched through using a plasma etch process to expose the contact plug, followed by deposition of a bottom electrode comprising a polysilicon, metal, or metal nitride. A chemical mechanical planarization (CMP) process is then used to planarize the surface, followed by deposition of a dielectric layer. However, when the spacer/liner is punched into the polysilicon layer, typically a contact clean must be performed to remove native oxide contaminants from the contact plug prior to deposition of the bottom electrode. Otherwise, the presence of native oxide on the contact could potentially inhibit current flow.
It is also desirable to perform a precleaning step when metal nitrides are used as the bottom electrode. A precleaning step is also desirable when forming a nano-laminate dielectric, where it is desirable to pre-clean the first dielectric material before a second dielectric material is deposited. Typically, aqueous etching solutions comprising HF or NH4F have been used in such cleaning operations. However, such solutions often result in the over etching of adjacent layers including the metal oxides or metal nitrides which comprise the sacrificial liner, bottom electrode, or other layers.
Accordingly, there is still a need in the art for a method of cleaning a substrate surface to remove native oxides and other contaminants without excessively attacking or removing metal oxides or metal nitrides from the substrate surface or adjacent exposed surfaces.